Such compressors are for instance described in U.S. Pat. No. 4,610,148, incorporated herein in its entirety, wherein two beds of adsorbents are used, which are arranged in a shell through which heat exchanging channels are arranged. The heat exchanging channels are connected to a closed circuit of heat exchanging fluid comprising a set of pumps, an additional heat exchanger with cooling action and a heat exchanger with heating action. The shell sides of these adsorbent beds are connected to a heat pump comprising a condenser, an expansion valve and an evaporator. These two beds each are connected both to the condenser and the evaporator side of the heat pump by means of check valves. Further examples of publications that discuss thermal waves in adsorption heat pumps are U.S. Pat. No. 4,637,218; Jones J. A. (Heat recovery systems & CHP 13(1993)363-371); Pons M., Applied thermal engineering, 16(1996)395-404); Sun L. M. et al. (Int. J. Heat mass transfer, 40(1997)281-293); Zheng W. et al. (Heat and mass transfer 31(1995)1-9); Wang, R. Z. (Renewable and sustainable energy reviews 5(2001)1-37); and Critoph, R. E. et al. (Applied Thermal Engineering 24(2004)661-678).
The beds in U.S. Pat. No. 4,610,148 comprise a zeolite, and the applied refrigerant or adsorbing vapor is water. The water vapor originating from the adsorption beds is guided through a set of check valves to a condenser of a heat pump. There the water vapor is condensed in a high pressure condenser, and the condensed water is guided through a pressure release valve, where due to the Joules Thomson effect, the temperature decreases substantially adiabatically, thus providing cooling capacity. In a low pressure evaporator, the water is re-evaporated and can be returned through a set of check valves to that adsorption bed that is cold and accepting the vapor to adsorb. The evaporator provides the actual thermal cooling power of the heat pump.
The adsorbing vapor is forced out of the solid adsorption material by heating the material with a heat transfer fluid. In order to have a substantially constant cooling power in the evaporator, two adsorption beds are chosen. One bed is heated to force out the adsorption vapor while the other is cooled down in order to provide re-adsorption of the adsorption vapor.
A series of check valves allows this alternating operation such that at substantially all times, high pressure vapor is provided to the condenser while relative low pressure vapor is retracted from the evaporator.
In order to increase efficiency in relation to batch cooling and batch heating of the adsorbing material, it was found that heating and cooling the solid adsorbing material by applying a moving temperature profile back and forth through the solid material substantially increased the heat pump performance. This pushing back and forth a temperature profile through the relatively elongated material is known as a thermal wave.
Application of such thermal wave has some further advantages, that only two adsorption cells are needed, a relative simple process flow diagram is needed and a relative uniform refrigerant mass flow over the entire cycle can be provided.
These systems are used because the driving heat can originate from low caloric waste heat or solar heat and the used adsorption vapors or gases can be chosen from non-freon types, which are harmless for the ozone layer.
Disadvantages of these systems are that the condenser, the evaporator and the two adsorbent beds are relative bulky in size. Since water is used as refrigerant, the whole system can only operate at reduced pressures, thus lowering the specific cooling power (SCP) of this system.
An alternative heat pump using zeolite as an adsorbent is presented in U.S. Pat. No. 4,637,218, incorporated herein in its entirety. In this system, again, water is used as a refrigerant medium. In this publication a shell-and-tube arrangement of the adsorption beds and mono block like arrangements of the adsorption bed are proposed. This system, again, suffers from the rather bulky size because of the relative low pressures applied for the evaporation and condensation of the water vapor.
P. Hu et al. (Energy Conversion and Management 50(2009)255-261) describe a refrigeration system comprising an adsorbent bed in an annular container, wherein the heat exchange fluid is on the inside.
A. Sateesh et al. (International Journal of Hydrogen Energy 35(2010)6950-6958) describe a single-stage metal hydride heat pump. This heat pump is based on an absorption process, wherein the metal hydride powder undergoes a chemical change. The term “absorption process” is generally reserved for processes based on chemical absorption, whereas “adsorption process” refers to physical adsorption.
Z. Dehouche et al. (Applied Thermal Engineering 18(1998)457-480) describe the thermal wave concept for a multi-hydride system. This system is also based on chemical changes, rather than physical changes in accordance with the present invention. Dehouche is based on absorption rather than adsorption and discloses a metal foam tube reactor. This type of reactor contains an aluminium foam matrix for improved heat transfer filled with metal hydride powder. The aluminium foam matrix is contained in an inner tube. The heat transfer fluid flows through an annular gap between the inner tube and an outer tube. The use of adsorbent material is not disclosed in Dehouche. To provide this adsorbent material in the form of a stack of pills is also not disclosed nor suggested by Dehouche.
R. E. Critoph et al (Proceedings of the Institution of Mechanical Engineering, 2000, Vol. 214, No. 5, Pages 439-448) relates to a prototype of fast cycle adsorption refrigerator utilizing a novel carbon-aluminium laminate. FIG. 4 shows an example of the laminate. The diameter of the stainless steel shell enclosing the laminate is 50 mm. These dimensions are not fit for the adsorption cell that is the object of the present invention, namely an adsorption cell suitable for a thermal wave operated adsorption compressor. Additionally, the heating and cooling of the known laminate is not performed in a heat transfer fluid channel in which a heat transfer fluid flows along the stainless steel shell. Instead, the known laminate is accommodated in a conventional heat pipe and the entire laminate is heated or cooled in batch without a thermal wave being formed in the generator.
WO01/69146 discloses a sorber that includes a plurality of disks of sorbent material such as sintered zeolite or ceramics. The disks are stacked together face-to-face. The disks may have grooves in one or both of its two faces which provide passageways between each adjacent pair of disks. Heating of the sorbent material may be effected by means of an electromagnetic wave generator, more particularly a magnetron or by conventional heaters. For the embodiment with the electromagnetic wave generator it is disclosed to locate between each pair of sorbent disks a electrically conductive disk. The conductive disks are metallic and are electrically coupled to an inner conductor or an outer housing which is also a conductor. More particularly, the successive ones of conductive disks are coupled alternately to either the inner conductor or the outer conductive housing so as to increase the magnitude of the electric field applied across the sorbent disks. WO01/69146 does not disclose that the sorber is intended and suitable for thermal wave operation. In fact, the only type of heating that is disclosed in WO01/69146 is bulk heating.